Wall form units and systems

ABSTRACT

A wall form unit for containing a pourable, curable construction material for forming a wall section integrating said wall form unit and said construction material, comprising a first panel and a second panels spaced apart in predetermined relation thereby forming a hollow between first and second panels for defining said wall section and at least one tie assembly having a spacer member for maintaining said first and second panel in predetermined relation, in which both the first panel and second panels are rigid and adapted to retain said construction material, wherein the first panel is constructed of a thermally insulating material and the second panel is constructed of a thermally conducting material. A wall form system for forming a section of wall and wall section and method for constructing same are also defined. The invention also relates to a panel for use in forming a wall form unit and also claims a kit for constructing a wall form unit.

This invention relates to wall form units and systems used to constructstructural components such as walls. More particularly, the presentinvention relates to thermally conducting panels for use in wall formunits and systems for constructing walls formed from pourable, curableconstruction material in which the form system remains in situ.

Construction components, such as walls and columns, are often made fromcurable construction materials such as concrete. It is well known tomake a specifically shaped component from such materials in order tobuild or erect civil engineering structures. Previously such forms wouldhave been typically made from materials such as wood. To make theconstruction component, the form is erected to create a cavity capableof holding the curable construction material, for instance concrete, ina liquid form. The concrete or other curable construction material isthen poured or otherwise introduced into the cavity created by the formand then allowed to set. Once the material has hardened into astructural component, the form is removed.

Alternatively, the form can be built from several form units, each formunit having a pair of spaced panels. The form units are placed adjacentto each other, both horizontally and vertically, to build a completeform. Enhanced efficiency in the construction of a form may be achievedin such a system. This is particularly the case where the form units aredesigned to remain permanently in situ, once placed, and do not have tobe removed once the concrete, or other curable construction material,has been poured and allowed to set. One such system has side panels foreach form unit made of an insulated material. These side panels performthe dual purpose of functioning as side units for the cavity, and thenafter the concrete has set, as an insulating layer on each side of theconcrete.

These wall form units and wall form systems are frequently referred toas Insulating Concrete Forms (ICFs). The use of Insulating ConcreteForms or more generally wall form units or systems is well accepted asvery effective building construction technology.

Typically an ICF or other wall form units or systems comprise anexpanded plastic (foamed plastic), usually expanded polystyrene orpolyurethane foam, form comprising two spaced apart panels or hollowblocks.

ICFs comprising two spaced apart panels will be generally supplied as aself assembly “flatpack” system comprising the two panels of foamedplastic and ties or other connecting components used for assembling theforms, hereinafter referred to as ties. ICFs are generally lockedtogether by a suitable connecting means, for instance by use of tongueand groove joints around the edges of the ICFs, as they are stacked toform walls. Steel rebars or reinforcing steel mesh can be used in thespace between the panels, into which concrete or other curableconstruction material is added, to provide added strength. When steelrebars are used then these can be in both horizontal and verticalorientation. The forms are assembled into a hollow vertical wall intowhich concrete or other curable construction material is poured therebycreating a solid wall. The ICF or wall form units remain in place andbecome a permanent part of the building and provide insulation. It hasbeen generally accepted that employing ICFs as a permanent part of thebuilding provides energy efficiency, contributing to environmentallyresponsible practices. As an alternative to delivering the ICFs to theconstruction site as a self-assembly “flatpack” the ICFs may also bedelivered as preassembled units. As a further alternative wall sectionsmay be built from the ICFs off site and these wall sections may bedelivered to the construction site where the building is to be erected.

Typical insulating concrete forms are described in Canadian patents1244668, 2551250, U.S. Pat. Nos. 4,703,602, 4,731,968, 4,949,515,5,704,180, 5,724,782, 5,809,728, 5,896,714, US published patentapplications 20040040240, 20040045237, 20080022619, Internationalapplications WO9525207, WO9901626, WO2008009103 and WO2008136819.

French patent 2598447 describes a structure comprising a light weightloadbearing framework. The framework includes cavities which are closedin on the sites by panels. A material is poured into the cavity in whichthe material with high heat storage capacity and quick setting time inorder to form a heat accumulator. An insulating layer is insertedbetween the external facing and the internal panel. Such a complexstructure employs several panels and limited capacity for theconstruction material without making the framework excessively deep andintrusive.

European patent application 1959212 describes a wall element formed fromglass plates with a core material consisting of microcapsules of phasechange material filling the space. However, such a wall element would becompletely unsuitable for retaining a curable construction material. Thefilling material incorporated in this wall element would not be curable.

PFSolutions describe cement bonded particle board used as a permanentformwork which is left in place after casting of concrete on-site ontheir website www.pfsolutions.ie. The cement bonded particle boardapparently has a thermal conductivity of 0.26 W/m·K. Nevertheless thesystem is devoid of any thermally insulating panel in direct contactwith the concrete core.

Although ICFs generally provide a multiple layer of insulation to walls,buildings constructed from ICF walls tend to suffer the disadvantage ofinadequate temperature regulation to rooms within the building. Theobjective of the present invention is to provide wall form units andsystems which overcome this problem. In particular it would be desirableto provide such wall form units and systems that are easilytransportable and can be installed easily on-site where the building orother construction can be erected.

According to the present invention we provide a wall form unit forcontaining a pourable, curable construction material for forming a wallsection integrating said wall form unit and said construction material,comprising a first panel and a second panel spaced apart inpredetermined relation thereby forming a hollow between the first andsecond panels for defining said wall section and at least one tieassembly having a spacer member for maintaining said first and secondpanels in predetermined relation, in which both the first panel andsecond panels are rigid and adapted to retain said constructionmaterial, wherein the first panel is constructed of a thermallyinsulating material and the second panel is constructed of a thermallyconducting material.

The invention also provides a wall form system for forming a wallsection having a core of pourable, curable construction materialsheathed by a plurality of panels comprising at least two wall formunits, each said wall form unit having means for interlocking said wallform units to define said wall section, a first panel and a secondpanels spaced apart in predetermined relation thereby forming a hollowbetween the first and second panels for receiving said constructionmaterial, and a least one tie assembly, said tie assembly comprising aspacer member for maintaining said first panel and said second panels insaid predetermined relation, in which both the first panel and secondpanels are rigid and adapted to retain said construction material,wherein the first panel is constructed of a thermally insulatingmaterial and the second panel is constructed of a thermally conductingmaterial.

In accordance with a further aspect of the invention we provide a kitfor constructing a wall form unit in accordance with the previouslystated aspects of the invention.

The invention also relates to a wall section comprising at least twowall form units or a wall form system as defined herein containing acured construction material between the first and second panel, whichcured construction material has been formed from a pourable, curableconstruction material that has been poured into the hollow between thefirst and second panels.

The wall section may often be formed on site where the building is to beerected. Alternatively the wall section may be formed at themanufacturer site and shipped to the location where the building is tobe constructed.

The invention also concerns a novel panel suitable for constructing awall form unit according to the aforementioned aspects of the inventionin which said panel is constructed of a thermally conducting material.

The present invention also relates to a process of erecting a buildingstructure which comprises a wall section formed from a plurality of ICFunits comprising the steps,

-   -   i) arranging the first and second panels of the plurality of ICF        units in predetermined relation for defining said wall section        such that a hollow is formed between the first and second panels        by spacing apart the first and second panels in predetermined        relation,    -   ii) connecting at least one tie assembly having a spacer member        for maintaining for spacing apart said first and second panels        in predetermined relation,    -   iii) introducing a pourable, curable construction material into        the hollow,    -   iv) allowing the pourable, curable construction material to        cure, in which both the first panel and second panel are rigid        and adapted to retain said construction material, wherein the        first panel is constructed of a thermally insulating material        and the second panel is constructed of a thermally conducting        material.

In constructing the wall form unit the second panels should be placed sothat they form the side of the wall that will face the interior of thebuilding and the first panels should be placed so that they form theside of the wall that will face the exterior of the building. The firstpanels and second panels should be maintained at a predetermineddistance using ties. Into the hollow created between the first andsecond panels the pourable, curable construction material e.g. concreteshould be introduced and allowed to set to form a wall section.

The pourable, curable construction material once introduced into thehollow should be in direct contact with the first and second panels.Once cured the pourable, curable construction material should form asolid core which is in direct contact with the first and second panels.

The inventors believe that by employing panels formed from a thermallyconducting material and a thermally insulating material respectivelyeach in direct contact with the cured construction material, forinstance concrete, the thermal mass of the cured construction materialcan be utilised and this provides for improved temperature regulationwithin rooms of buildings whilst maintaining adequate insulation. Theinventors believe that the reason that the buildings constructed fromthe prior art ICF walls tend to suffer the disadvantage of inadequatetemperature regulation to rooms within the building is because of theirlack of accessible thermal mass.

The pourable, curable construction material which sets to form theinternal core of cured construction material, typically concrete,exhibits high thermal mass.

Generally the thermal mass, expressed in terms of specific heatcapacity, will be at least 700 J/kg·K and usually at least 800 J/kg·Kor, more preferably, at least 900 J/kg·K for instance as much as 1000J/kg·K or 1100 J/kg·K or more. The density of the concrete will have abearing on the heat capacity in volume terms. The higher the density,the greater is the volumetric heat capacity. It is therefore preferableto use cured construction materials, typically concrete based onPortland cement, which have a high density. The density is generallyalways >0.5 kg/litre, preferably >1.0 and most preferably >2.0. Thepourable, curable construction material once cured and solidified maydesirably have an admittance value of between 1 and 6 W/m²·K. Anyconcrete normally used for construction purposes may be used inaccordance with the present invention but concrete designed specificallyfor ICF applications, such as Rheo Cell (Trade Mark) ICF concrete fromBASF or U Crete (Trade Mark) from Bardon Concrete are preferable.Waterproof concrete may also be used especially for basementconstruction. It may also be desirable to include phase change material(PCM) to provide additional temperature regulation within the building.Suitable phase change materials are described herein in regard to thesecond panel.

The dimensions of the first and second panels may be typical of ICFdimensions commonly used. Suitably the panels may be between 1000 mm and1500 mm in length, preferably between 1200 and 1300 mm, for instancearound 1220 mm. The height of the first panel and second panel may bebetween 350 and 500 mm, preferably between 390 and 450 mm, for instancearound 400 to 410 mm. However, in some situations it may be desirable touse larger dimensions. For instance, it may be desirable for the panelsto be as much as 3000 mm or 4000 mm in length and/or width or larger.Even larger dimensions could be used if it is found to be practicable.Even larger dimensions may for instance be up to 10,000 mm in height andup to 20,000 mm in length.

The use of large dimensions include ICF structures, which could bepreconstructed in a factory. Typical larger dimension IFC structureswould be analogous the dimensions employed in HercuWall™, made byHercuWall Inc (USA).

Generally the first and second panels should be strong and sufficientlyhard wearing to avoid being easily damaged during transportation orespecially on the construction site. This would include during handling,assembly, pouring of concrete, during curing of the concrete, mechanicaland electrical fixing and subsequent finishing, decoration etc.

The edges of the first and second panels may be formed to allow the wallform units (ICFs) to be stacked such that both horizontal and verticaledges lock into the neighbouring units. The locking system may be basedon tongues and grooves. This may be achieved by for instance providingthe upper edge and left side with a tongue and the lower edge and rightside with a groove such that each panel may interlock with thisneighbouring panel. These locking systems may be added, cast or cut intothe panels during manufacture or alternatively may be formed by fixingseveral thinner panels together to form the tongues and grooves.

The first and second panels may be further adapted in order tofacilitate better adhesion to the concrete. For instance this may beachieved by applying grooves or other surface formations on the sides ofthe panels intended to face the concrete or other curable/curedconstruction material. These grooves, on the second panels, should alsofacilitate improved thermal contact between the panel and the concrete.

The surface of the second panel facing the interior of the building,i.e. the opposite side to that in contact with the concrete or othercurable/cured construction material, may also be adapted for aparticular purpose required for the interior of the building. Forinstance the interior facing surface of the second panels may be smoothin order to accept paint or wallpaper or alternatively it may be brushedor roughened in order to accept tiles or any other covering where asurface key is desirable. The second panel may also be faced withsuitable scrim e.g. of glass fibre to improve surface finish, strengthor fire resistance properties.

The first panel of the wall form units or systems may be anyconventional panel used for forming ICFs. Typically the first panel maybe constructed from a composite material, a polymer or a polymer-basedcompound. Suitably the first panel is formed from a foamed plastic,preferably an expanded polystyrene (for example Styropor (Trade Mark)from BASF) or polyurethane foam. The first panel may contain otherinsulating components with the foamed plastic, for instance Aerogel(Trade Mark) or vacuum panel insulation. Additives may be incorporatedinto the foamed plastic of the first panel to improve performance suchas strength or insulation characteristics. Suitable additives for foamedplastic include graphite, for instance Neopor (Trade Mark), which is agraphite-containing expanded polystyrene maufactured by BASF. The firstpanel may contain two or more layers of foamed plastic thereby forming acomposite form. The thickness of the first panel will be determined bythe particular insulation value which is required for the particularbuilding being constructed. Suitably the first panel may have a thermalconductivity below 0.045 W/m·K. Generally the thermal conductivity canbe any value below this and may be as low can be measured. It ispossible that the thermal conductivity may be as low as 0.005 W/m·K.Typically the thermal conductivity of the first panel may be in therange of 0.010 and 0.040 W/m·K often within the range 0.020 and 0.040W/m·K.

The second panel may be constructed from any material that provides theright characteristics for use in the wall form units and system. Itshould be rigid and adapted to retain the construction material such asconcrete. Furthermore, it should desirably possess a thermalconductivity of least 0.1 W/m·K (Watts per metre Kelvin) at least in thedirection of the thickness of the panel, and preferably at least 0.2W/m·K. In some cases the thermal conductivity of the second panel may beat least 0.25 W/m·K, at least 0.3 W/m·K, at least 0.4 W/m·K andpreferably at least 0.5 W/m·K and more preferably at least 1.0 W/m·K.There is no upper limit to the thermal conductivity provided that theother properties such as rigidity and strength are not compromised. Thethermal conductivity may be up to 100 W/m·K.

The second panel may be constructed from any suitable metal in the formof a metal sheet for instance. Typically this may be aluminium or copperhaving thermal conductivities of 200 W/m·K and 380 W/m·K respectively.However, it is preferred that the second panel is constructed fromsuitable building materials which have been adapted to improve thethermal conductivity.

Second panels potentially include concrete panels or blocks, stone ormarble panels or boards comprising cement, such as Portland cement ormagnesia cement e.g. fibre board or particle board. Plasterboard may beused if it is made sufficiently durable such that it is not damagedduring the construction process. Standard plasterboards are generallynot suitable for this application.

Preferably the second panel comprises a combination of at least twocomponents comprising a first component which is selected from inorganicbinders, a polymer and a polymer-based compound and a second componentselected from thermally conducting particles, filaments or mesh whichare distributed throughout the first component.

Preferred first components of the second panel include inorganichydraulic binders such as are found in cement-based boards, for instancePortland cement, particularly magnesia cement boards such as those basedon magnesium oxysulphate, magnesium oxychloride and magnesium phosphate.Hydraulic inorganic binders are for instance inorganic materials thatreact with water to form solid matrices. Other examples includemagnesium oxide, calcium oxide, calcium hydroxide/pozzolana mixtures,calcium aluminate cements, gypsum plaster etc. Non-hydraulic inorganicbinders may also be used as the first component of the second panel.Such binders harden by completely or partially drying out, and includecalcium hydroxide, calcium carbonate, clay, magnesium hydroxide etc.Blends may also be used and it is preferred that an inorganic bindercontains at least one hydraulic binder.

The second component of the second panel will include materials thathave high thermal conductivity. In order to provide the second panelwith sufficient thermal conductivity the second component materials willdesirably have thermal conductivities of at least 0.1 W/m·K andpreferably at least 0.2 W/m·K. It is particularly preferred that thesecond component materials possess thermal conductivities in excess of1.0 W/m·K and especially in excess of 2.0 W/m·K. there is no maximumlimit of the thermal conductivity of the second component and this maybe as high 200 or even 500 W/m·K.

Preferably, the second component of the second panel can be any of thematerial is selected from the group consisting of graphite, aluminaparticles, silica sand, fine gravel or stone particles, metallic fibres,metallic mesh and metallic particles. Suitable metals include iron,copper, aluminium or metal alloys such as steel or brass. Other metalsor metal alloys may be used such as lead, tin, bronze, silver etc.

The second component of the second panel may be in the form ofparticles, fibres or other structure, such as mesh. Typically theparticles may be relatively fine having weight average particle sizediameters of below 1 mm, especially below 0.1 mm and for instance as lowas 0.01 mm or below. Alternatively the particles may be relativelycoarse having weight average particle size diameters of at least 1 mmand even at least 2 mm, for instance up to 5 mm or even up to 10 mm or20 mm or more. The fibres may have cross-sectional diameters of between0.01 mm and 1 mm or higher. The lengths of the fibres may be relativelyshort, for instance less than 5 mm or sometimes may be as much as 10 mmor 20 mm and considerably longer if in the form of a wool, for instancesteel wool or steel mesh.

The second panel may comprise the first component in an amount between 5and 100% by weight of the two components (not including any fillers orlining materials such as paper or scrim) and the second component in theamount of between 0 and 95% by weight of the panel. Typically the secondcomponent may be present in the panel in an amount between 5 and 95% byweight whilst the first component may be present in an amount of between5 and 95% by weight. In many systems the second component can be themajor component, for instance between 65 and 95% by weight, preferablybetween 75 and 85% by weight and the first component can be between 5and 35% by weight, preferably between 15 and 25% by weight. Preferablythe first component will form a matrix within the panel throughout whichthe second component is distributed. Should the second panel have highthermal conductivity, say >0.1 W/m·K, then a second component may not benecessary.

The second panel may be constructed from a material which containspartial aeration, for instance pumice, provided that the aeration doesnot compromise the thermal conductivity and ability to contain thepourable, curable construction material. Generally the material used toform the second panel desirably should not contain significant amountsof air voids, for instance by aeration as this may tend to yield lowerthermal conductivity. Desirably the second panel should be as dense asit is practicable within the normal constraints of panel manufacturing,construction of the building and use of the building. Desirably thesecond panel has a density of at least 100 kg/m³ and preferably at least300 kg/m³ and more preferably at least 700 kg/m³. Especially preferredmaterials tend to have densities of at least 1000 kg/m³ and often asmuch as 1500 kg/m³. Nevertheless, the density may be significantlyhigher, for instance up to 1750 kg/m³ or even up to 2400 kg/m³ or more.

An example of a second panel is one formed from Portland cement ormagnesia cement as the first component comprising particles of sand orfine aggregate as the second component which is distributed throughoutthe Portland cement or magnesia cement. Suitably the sand or fineaggregate will form between 65 and 95% of the total weight of the secondpanel the remainder being the magnesia cement. Preferably the sand orfine aggregate will form between 75 and 85% of the total weight of thesecond panel and the magnesia cement will form between 15 and 25% bytotal weight.

The second panel may also contain other components such as fillers orstrengthening fibres. Such fillers may for instance be included wherethe second panel is based on a hydraulic inorganic binder such asmagnesia cement. Typically this may include wood particles or fibres,synthetic fibres glass, basalt or carbon fibres or carbon particles.However, the aim must be to maximise the overall thermal conductivity ofthe second panel, and the addition of fillers, fibres etc must beconsidered carefully with this aim in mind. A balance must be foundbetween achieving a suitably high thermal conductivity and achievingrequirements such as strength, appearance, cost etc.

In a preferred form of the invention the second panel may contain phasechange material (PCM). This feature will allow further temperatureregulation of rooms within the building.

Suitable phase change materials may be organic, water insolublematerials that undergo solid-liquid/liquid-solid phase changes at usefultemperatures (typically between 0 and 80° C.). Generally the enthalpy ofphase change (latent heat of fusion and crystallization) is high.Suitable organic phase change materials exhibit a high enthalpy of phasechange, typically >50 kJ/kg, preferably >100 kJ/kg and mostpreferably >150 kJ/kg when determined by Differential ScanningCalorimetry (DSC).

Suitable organic phase change materials include (but are not limited to)substantially water insoluble fatty alcohols, glycols, ethers, fattyacids, amides, fatty acid esters, linear hydrocarbons, branchedhydrocarbons, cyclic hydrocarbons, halogenated hydrocarbons and mixturesof these materials. Alkanes (often referred to as paraffins), esters andalcohols are particularly preferred. Alkanes are preferablysubstantially n-alkanes that are most often commercially available asmixtures of substances of different chain lengths, with the majorcomponent, which can be determined by gas chromatography, between C₁₀and C₅₀, usually between C₁₂ and C₃₂. Examples of the major component ofan alkane organic phase change materials include n-octacosane,n-docosane, n-eicosane, n-octadecane, n-heptadecane, n-hexadecane,n-pentadecane and n-tetradecane. Suitable ester organic phase changematerials comprise of one or more C₁-C₁₀ alkyl esters of C₁₀-C₂₄ fattyacids, particularly methyl esters where the major component is methylbehenate, methyl arachidate, methyl stearate, methyl palmitate, methylmyristate or methyl laurate. Suitable alcohol organic phase changematerials include one or more alcohols where the major component is, forexample, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, andn-octadecanol.

It is also possible to include a halogenated hydrocarbon along with themain organic phase change material to act as a fire retardant.

Organic phase change materials are substantially water insoluble, asthis is necessary for preparing particulate forms of the organic phasechange material, for instance in emulsion form or encapsulated form.

Organic phase change materials are utilized in the invention in aparticulate form, by which is meant either in emulsified or encapsulatedform. For reasons discussed in more detail below, the particle size ofphase change material particles should not be too large. Typically thephase change material particles are as small as possible within certainlimitations. This is discussed in more detail below when considering thephase change material form, for instance in emulsion or encapsulatedform.

In order to provide the composition of the invention where the organicphase change material is not encapsulated it is generally desirable toprovide the organic phase change material in the form of an emulsion.Suitable emulsions comprise of a disperse phase of organic phase changematerial stabilized in an aqueous continuous phase, hence it is a typeof oil-in-water or O/W emulsion. The term “emulsion” is often applied toliquid-in-liquid two phase systems. In this invention we allow the term“emulsion” to embrace both the liquid-in-liquid and solid-in-liquidsystems depending on whether the particles of phase change material areliquid (molten) or solid (crystallized). Hence the term “particles”,when referring to the organic phase change material, also embraces boththe liquid and solid form. In a suitable emulsion, monomeric and/orpolymeric surfactant(s) is/are used to facilitate emulsification of theorganic phase change material and stabilize the particles in the aqueouscontinuous phase.

The particle size of an emulsion is generally limited to a fairly narrowrange. Large oversized particles, especially very coarse particles,should be avoided since they tend to be more unstable and more prone tocoalescence and hence phase separation. Thus, for practical reasons, theparticle size of the organic phase change material in an emulsion formis typically between 0.05 μm and 50 μm, often between 0.1 μm and 20 μmand more often between 0.5 μm and 10 μm (expressed as volume meandiameter as determined, for example, by a Sympatec particle-sizeanalyzer). Therefore this definition includes emulsions described asmicroemulsions and nanoemulsions.

Preferably the emulsions will contain at least 20% w/w particles oforganic phase change material and more preferably this will be at least40% w/w. The emulsion may contain up to 75 or 80% w/w, although usuallynot more than 60 or 65% w/w.

Normally the emulsions should be suitably stable in that they should notphase separate after several hours in static storage; preferably theywill be stable for at least 7 days and most preferably for at least 30days. Often the emulsions are stable for several weeks or months andeven up to one year or more. Although there may be a tendency forparticles to migrate towards the surface of the storage container (aneffect known as “creaming”), a good emulsion will not destabilize toform a substantial layer of coalesced phase change material and stirringwill substantially rehomogenize the creamed particles.

Suitable emulsions may be prepared by conventional methods such as thosedescribed in the book “Emulsion Science” by Philip Sherman. A usefulguide to monomeric surfactant (emulsifier) selection is given in apublication by ICI entitled “The HLB System”. Numerous other literaturearticles describe the preparation of stable emulsions, including theselection and amount of monomeric and/or polymeric surfactant(s) to beused.

Note that it is generally preferred to prepare the emulsion using theliquid form of the organic phase change material i.e. in a molten state.Organic phase change materials that contain an additive such as ahalogenated paraffin, organic nucleating agent, oil soluble surfactantetc should also be in a fully liquid state, ideally. It is preferable tomaintain the organic phase change material (including optionaladditives) in a liquid state during the formation of the emulsion, whichusually involves maintaining the temperature of the organic phase changematerial (including optional additives) above the temperature where waxcrystals may form. The formation of an emulsion involves the combinationof a disperse phase comprising the organic phase change material to anaqueous phase and it is sometimes necessary to control the temperatureof the aqueous phase prior to and/or during the addition of the organicphase change material. This is to avoid cooling the disperse phase to apoint where problematical crystallization can occur.

Typically encapsulated organic phase change materials comprise theorganic phase change material and optional additives such as ahalogenated paraffin or a nucleating agent which is surrounded by ashell that is impermeable to the phase change material. Unlike free(unconstrained) particles of organic phase change material, capsuleparticles remain as solid particles even when the organic phase changematerial in the core of the capsules is in its higher energy moltenstate. In capsule form the organic phase change material is completelysurrounded and entrapped by the shell and is protected againstcontamination. When the shell is robust, the organic phase changematerial is more securely contained and less likely to escape from thecapsules and compositions comprising capsules. For this reason it ispreferred to use capsules in this invention, particularly capsules thatare robust. Details of the robust character of the capsules are providedbelow.

Since encapsulated organic phase change materials tend to be stable,solid entities, they can be provided in a broader range of particlesizes than would be possible for the aforementioned emulsified organicphase change materials. It is possible to use capsules in this inventionwith mean primary particle size of between 0.1 μm and 1 mm. Generally,it is preferred to use smaller capsule particle sizes in this inventionfor a number of reasons. Smaller primary capsules tend to be moredurable leading to inventive compositions which do not readily releaseorganic phase change material. Due to their greater surface/volumeratio, smaller particle sizes are expected to give inventivecompositions which more readily transfer heat to/from the particles oforganic phase change material. It is generally possible for smallercapsules to be more uniformly distributed throughout the second panel.

Capsules may conveniently be used in the form of an aqueous dispersionor dry powder.

Suitable aqueous dispersions typically comprise 30 to 60% w/w, mostpreferably 40 to 50% w/w microcapsules. When provided as an aqueousdispersion, the particle size of capsules of organic phase changematerial should be carefully considered. In addition to the benefits ofsmaller capsules discussed earlier, dispersions of smaller capsules tendto exhibit the favourable property of better stability (reduced capsulecreaming or settling) and the unfavourable property of increasedviscosity compared to a dispersion of larger sized capsules at anequivalent concentration. It is also generally more difficult to preparesuitable capsules with very small particle sizes and/or the processrequired is more costly due to the extra processing that is requiredand/or the use of more specialized equipment. A balance must be foundbetween these advantages and disadvantages and a volume mean diameter(VMD) of capsules (when in the form of an aqueous dispersion) of between0.2 μm and 20 μm is usually chosen. Preferably the VMD of the capsulesin an aqueous dispersion is between 0.7 μm and 10 μm and more preferablybetween 1 μm and 5 μm. VMD is determined by a Sympatec Helos particlesize analyzer or another technique found to give results formicrocapsules that are in very good agreement with the results from aSympatec Helos analyzer.

Capsules in a dry form may also be used in this invention. Such capsulesmay be obtained when an aqueous dispersion or suspension of capsules issubjected to a water removal step, which may include spray-drying,air-drying, filtration or centrifugation. It is also possible topartially remove the water to produce a paste or cake form of thecapsules. Spray-drying is particularly preferred when producingessentially dry products from a dispersion of microcapsules up to 10 μmin VMD. Preferably the particle-size of the capsules to be spray-driedis 1 μm to 5 μm. Spray-dried particles of organic phase change materialcomprise of 1 or more primary particles (microcapsules), and oftenseveral primary particles in an agglomerated form. The VMD of thespray-dried particles is generally 5 μm to 200 μm, preferably 10 μm to100 μm and more preferably 20 μm to 80 μm. This range balances theadvantages of small particle sizes with the need to avoid dust andassociated respiratory hazards.

It is preferable to use the aqueous dispersion form of capsules in thisinvention as this usually provides the preferred smaller capsuleparticle sizes and, as the water removal step needed for the dry productis avoided, at a lower cost. It is noted that typical microencapsulationprocesses provide an aqueous capsule dispersion as a product of theprocess.

The encapsulation process results in capsules with a substantiallycore-shell configuration. The core comprises of organic phase changematerial and the shell comprises of encapsulating polymeric material.Usually the capsules are substantially spherical. Preferably the shellis durable such that the organic phase change material is protected fromcontamination and cannot easily escape from the capsules.Thermogravimetric analysis (TGA) provides an indication of therobustness of the capsules. “Half Height” is the temperature at which50% of the total mass of dry (water-free) capsules is lost as a fixedmass of dry capsules is heated at a constant rate. In this analysismethod mass may be lost due to organic phase change material escaping asvapour permeating through the shell and/or due to rupturing of theshell. Particularly suitable microcapsules of organic phase changematerial (in the 1 μm to 5 μm mean particle size range) have a HalfHeight value greater than 200° C. or 250° C., preferably greater than300° C. and more preferably greater than 350° C., when TGA is carriedout under a nitogen atmosphere using a Perkin-Elmer Pyris 1 at a rate of20° C. per minute using typically 5 to 50 mg of dry sample. The drysample is obtained by adding a quantity of the dispersion product(usually at 45% w/w solids content) to the sample pan of the analyzerand then holding the temperature at 110° C. to remove the water (the drystate has been reached when stable readings are obtained at 110° C.).The analysis then proceeds by increasing the temperature at a rate of20° C./minute.

Microcapsule products in powder form, obtained from a spray-dryingprocess as described earlier, for example, may be analyzed in the sameway. In this case the drying step is usually very short as the powder isessentially dry.

Capsules may be formed by any convenient encapsulation process suitablefor preparing capsules of the correct configuration and size. Variousmethods for making capsules have been proposed in the literature.Processes involving the entrapment of active ingredients in a matrix aredescribed in general for instance in EP-A-356,240, EP-A-356,239, U.S.Pat. No. 5,744,152 and WO 97/24178. Typical techniques for forming apolymer shell around a core are described in, for instance, GB1,275,712, 1,475,229 and 1,507,739, DE 3,545,803 and U.S. Pat. No.3,591,090.

The phase change material may be applied to one or more surfaces of theformed second panel, preferably to the surface facing the interior ofthe building. More preferably, however, the phase change material isincorporated into the matrix of the second panel during its manufacture.In fact the major component, e.g. first component, of the second panel,preferably magnesia cement, will desirably form a matrix in which thephase change material is surrounded. More preferably both firstcomponent, preferably magnesia cement, and the second component,preferably sand or fine aggregate, will surround the phase changematerial. In particular the phase change material may be uniformlydistributed throughout both the first component, e.g. magnesia cement,and second component, e.g. sand or fine aggregate of the second panel.

The phase change material may be incorporated during the production ofthe second panel or applied to the surface of the formed second panel inwhich the phase change material may be in the form of a dispersion orslurry in a continuous phase liquid. Typically this may be a dispersionor slurry in water or for instance in the form of an aqueous emulsion.Preferably the phase change material is microencapsulated and is appliedas an aqueous dispersion. Alternatively the phase change material may beapplied in the form of dried microcapsules.

The second panel may contain flame retardant additives and this mayinclude inorganic salts or other inorganic compounds such as magnesiumhydroxide, aluminium hydroxide or borates.

The thickness of the second panel may be between 5 and 50 mm, preferablybetween 5 and 30 mm, more preferably between 10 and 20 mm.

The first and second panels may be fitted with suitable anchor pointsfor the internal ties. The tie anchors may be cast into the foamedplastic during manufacture. Where the first panel is constructed fromsome other material other means for securing the anchor points may bemore appropriate, for instance screws or other standard fixing means.

The ties may be any conventional ties used in ICFs or other wall formunits are described in the prior art, for instance as referred toherein. Typically the ties can be constructed from metal or plastic.Where the ICFs are not based on the “flat pack” system but form anintegrated block, the ties may be constructed of foamed plastic. Theties should desirably incorporate a spacer member which maintains thepredetermined distance of the first and second panels. Typically theties and spacer member will form an integrated entity and desirably willbe constructed from metal or plastic, or foamed plastic as given above.It may be desirable to integrate the ties with the first and secondpanels to form an integrated block. Tie anchors may be cast into thepanels, particularly the first panel. The first and/or second panel maycontain slots where the ends of the ties are inserted and secured. Inthis case the ties may be permanently connected to one panel andconnected to the other panel by inserting the free end of the ties intoslots in the other panel. Alternatively the ties may be fitted intoslots in both panels. Two or more types of ties may be used.

According to one aspect of the present invention the wall form unit(e.g. ICF) is assembled by interconnecting a multiplicity of firstpanels together and a multiplicity of second panels together, thusformed assembly of first panels and thus formed assembly of secondpanels being maintained in a predetermined distance by a suitable tieassembly. The hollow section formed between the assembly of first panelsand the assembly of second panels, hereafter referred to as the cavity,may be between 50 and 500 mm in spatial distance between the twoassemblies. Preferably the cavity may have an interspatial distance ofbetween 100 and 220 mm. Typical cavity interspatial distances can forinstance be 102 mm, 158 mm, and 203 mm depending upon the buildingstructure required. Other pre-formed sections, such as corners, may alsobe made according to this invention.

The above described embodiments of the invention are intended to beexamples of the present invention and alterations and modifications maybe affected there to, by those skilled in the art, without departingfrom the scope of the invention which is specified in the claims.

FIG. 1 shows a wall section according to the present invention having afirst panel (1) of a thermally insulating material on the exterior sideof the wall section; a metal rebar (2) for wall supporting strength; atie (3) for maintaining the first and second panels spaced apart inpredetermined relation; a corner post (4); a second panel (5) ofthermally conducting material located on the interior side of the wallsection; and concrete (6) as a pourable, curable construction material.

1. A wall form unit, comprising: a first panel comprising a thermallyinsulating material, a second panel comprising a thermally conductingmaterial, a hollow between the first and second panels, and at least onetie assembly comprising a spacer member for maintaining the first andsecond panels spaced apart in predetermined relation, in which both thefirst panel and the second panel are rigid and adapted to retain aconstruction material.
 2. The wall form unit of claim 1, wherein thefirst panel comprises: a composite material and a polymer or apolymer-based compound.
 3. The wall form unit of claim 1, wherein thesecond panel comprises: a first component comprising an inorganicbinder, a polymer or a polymer-based compound.
 4. The wall form unit ofclaim 1, wherein the second panel comprises: a first componentcomprising an inorganic binder, a polymer or a polymer-based compoundand a second component comprising graphite, an alumina particle, silicasand, a fine gravel particle, a stone particle, metallic fiber, metallicmesh, or a metallic particle.
 5. The wall form unit of claim 1, whereinthe second panel comprises a hydraulic inorganic binder.
 6. The wallform unit of claim 1, wherein the second panel comprises magnesiacement.
 7. The wall form unit of claim 1, wherein the second panelcomprises magnesia cement comprising particles of sand, or otheradditive of high thermal conductivity, distributed throughout themagnesia cement.
 8. The wall form unit of claim 1, wherein the secondpanel comprises phase change material (PCM).
 9. The wall form unit ofclaim 1, wherein the second panel comprises phase change material (PCM)and magnesia or magnesia cement.
 10. The wall form unit of claim 8,wherein the phase change material (PCM) is microencapsulated.
 11. A wallform system, comprising: a core comprising pourable, curableconstruction material; a plurality of panels sheathing the core, whereinthe plurality of panels comprises at least two wall form units adaptedfor interlocking and wherein each wall form unit comprises a first paneland a second panel in predetermined relation, thereby forming a hollowbetween the first and second panels for receiving the constructionmaterial; and at least one tie assembly comprising a spacer member formaintaining the first panels and the second panels in predeterminedrelation, wherein both the first panels and the second panels are rigidand adapted to retain the construction material, the first panelcomprises a thermally insulating material, and the second panelcomprises a thermally conducting material.
 12. A kit comprisingcomponents suitable for constructing the wall form unit of claim
 1. 13.A wall section, comprising at least two of the wall form units of claim1, and a cured construction material in the hollow between the first andsecond panels comprising a poured, cured construction material.
 14. Aprocess of erecting a building structure, comprising: i) arranging afirst panel and a second panel of a plurality of Insulating ConcreteForm (ICF) units in predetermined relation for defining a wall section,such that the first and second panels are spaced apart to form a hollowbetween them, ii) connecting at least one tie assembly comprising aspacer member for maintaining the first and second panels inpredetermined relation, iii) introducing a pourable, curableconstruction material into the hollow, and iv) curing the pourable,curable construction material, wherein both the first panel and thesecond panel are rigid and adapted to retain the construction material,the first panel comprises a thermally insulating material, and thesecond panel comprises a thermally conducting material.
 15. The wallform unit of claim 2, wherein the polymer or polymer-based compoundcomprises an expanded polystyrene or polyurethane foam.
 16. The wallform unit of claim 3, wherein the second panel further comprises asecond component distributed throughout the first component, the secondcomponent selected from the group consisting of a thermally conductingparticle, a filament, and a mesh.
 17. The wall form unit of claim 9,wherein the phase change material (PCM) is microencapsulated.
 18. A wallsection comprising the wall form system of claim
 11. 19. The wall formunit of claim 16, wherein the second component comprises iron, copper,aluminum, lead, tin, silver, or a metal alloy.
 20. The wall form unit ofclaim 16, wherein the first component forms a matrix within the panel,and wherein the second component is distributed throughout the matrix.